Synergistic additive combination for industrial gear oils

ABSTRACT

The invention relates to industrial gear oil compositions that have been specially designed to have improved friction and/or antiwear properties. That is the industrial gear oil compositions of the invention provide good performance and/or protection in the areas of friction and/or antiwear due to the use of a synergistic combination of additives. The industrial gear oil compositions of the invention utilize a combination of certain phosphorus-containing compounds and derivatives of a hydroxy-carboxylic acid, to provide a synergistic improvement in friction and/or antiwear properties.

The invention relates to industrial gear oil compositions that have been specially designed to have improved friction and/or antiwear properties. That is the industrial gear oil compositions of the invention provide good performance and/or protection in the areas of friction and/or antiwear due to the use of a synergistic combination of additives. The industrial gear oil compositions of the invention utilize a combination of certain phosphorus-containing compounds and derivatives of a hydroxy-carboxylic acid, to provide a synergistic improvement in friction and/or antiwear properties.

BACKGROUND OF THE INVENTION

Industrial gearboxes see extreme operating conditions that can lead to damage, for example, wear to the internal components of the gearbox. This damage reduces the life of the industrial gearbox and can lead to costly and prolonged maintenance, repair costs, unscheduled downtime for the equipment that contains the industrial gearbox, and similar problems.

There is an on-going need for improved industrial gearbox lubricants that can provide better performance in and protection of industrial gearboxes, thus extending the service life of the industrial gearboxes and the equipment that contains them.

One means of protecting an industrial gearbox and extending the life of the fluid lubricating them is to reduce the temperature at which it operates. It is generally known that extended exposure to the high temperatures that industrial gearboxes commonly operate under increases the wear and tear on the components of the gearboxes, eventually leading to failure. This negative impact of high operating temperature is the result of multiple forces, including but not limited to the fact that the high temperatures can accelerate the break-down of the protective additives and increase the oxidation of the base fluid present in the industrial gearbox lubricant, thus leaving the parts of the gearbox less protected over time. Reducing the operating temperature of an industrial gearbox will result in improved performance over time.

One means of reducing the operating temperature of an industrial gearbox is by use of an external cooler or the addition of radiating fins. However, such approaches have limitations and can involve costly and time consuming modifications to existing equipment. There is a need for an approach that reduces the operating temperature of an industrial gearbox in existing equipment without the need for such modifications.

An alternative to reducing gearbox operating temperature would be to operate the equipment at a lower level (lower load, lower power, lower speed, etc.). However, this approach generally leads to a reduction in production and/or efficiency and so is not an attractive option to equipment operators trying to maintain productivity. Instead there is a need for industrial gearbox lubricants that can reduce the operating temperature of an industrial gearbox without sacrificing operation levels (equipment load, power, speed, etc.).

Thus there is a need for improved industrial gearbox lubricants that can reduce the operating temperature of the industrial gearboxes in which they are used, thus improving the performance of the industrial gearboxes.

Another means of protecting an industrial gearbox and extending the life of the fluid lubricating them is to improve the protection the moving parts have from friction and wear, which can lead to part failure and shorter service life.

Thus there is a need for improved industrial gearbox lubricants that can better protect the moving parts of the industrial gearbox from friction and wear, thus improving the performance of the industrial gearboxes.

It has now been found that the industrial gearbox lubricant compositions of the present invention, which utilize a synergistic combination of additives, can provide a reduction in industrial gearbox operating temperature and/or better protection the moving parts of the industrial gearbox from friction and wear, with no other changes to equipment operating conditions.

SUMMARY OF THE INVENTION

The invention provides industrial gear oil compositions designed to provide improved friction performance while still providing comparable wear protection. Improved friction performance can result in reduced operating temperatures, which can reduce high temperature related wear on lubricants and equipment and extend the service life of the fluid and/or equipment.

The invention provides an industrial gear oil composition that includes: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid, where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight, and component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more. In some embodiments component (b) is present in the industrial gear oil composition at no more than 5 percent by weight, and in other embodiments at no more than (or even less than) 4, 3, 2.5, 2, 1.75, 1.2 or even 1 percent by weight of the overall composition. In some embodiments component (b) and component (c) combined are present in the industrial gear oil composition at no more than 10 percent by weight, and in other embodiments at no more than 5, 4, or even 3 percent by weight of the overall composition. In some embodiments component (b) is present in the industrial gear oil composition from 0.3 to 1.2 percent by weight, or from 0.3 to 1.1, or from 0.3 to 1.0 percent by weight.

The invention provides for the industrial gear oil compositions described herein where the oil of lubricating viscosity includes mineral base oil.

The invention provides for the industrial gear oil compositions described herein where the oil of lubricating viscosity includes synthetic base oil and/or fluid.

The invention provides for the industrial gear oil compositions described herein where the phosphorus-containing compound includes an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, phosphonates, or some combination thereof. In some embodiments a triphosphate is used in combination with the phosphorus-containing compound described herein. In other embodiments the phosphorus-containing compound is free of any a triphosphates.

The invention provides for the industrial gear oil compositions described herein where the phosphorus-containing compound includes alkyl phosphites.

The invention provides for the industrial gear oil compositions described herein where the derivative of a hydroxy-carboxylic acid, includes a compound derived from a hydroxy-carboxylic acid represented by the formula:

wherein: a and b may be independently integers of 1 to 5; X may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y may be independently —O—, >NH, or >NR³ or two Y's together representing the nitrogen of an imide structure R⁴—N< formed between two carbonyl groups; and each R³ and R⁴ may be independently hydrogen or a hydrocarbyl group, provided that at least one R¹ and R³ group may be a hydrocarbyl group; each R² may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR² group is located on a carbon atom within X that is α or β to at least one of the —C(O)—Y—R¹ groups, and further provided that at least on R² is hydrogen.

The invention provides for the industrial gear oil compositions described herein where the derivative of a hydroxy-carboxylic acid, comprises a compound derived from a hydroxy-carboxylic acid represented by the formula:

wherein each R⁵ is independently H or a hydrocarbyl group, or wherein the R⁵ groups together form a ring, and where the hydroxy-carboxylic acid is reacted with an alcohol and/or an amine, via a condensation reaction, to form the derivative of the hydroxy-carboxylic acid.

The invention provides for the industrial gear oil compositions described herein where the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid.

The invention provides for the industrial gear oil compositions described herein where the composition further comprises (d), one or more additional additives. Component (d) may include one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.

The invention provides for the industrial gear oil compositions described herein where the weight ratio of component (b) to component (c) in the industrial gear oil composition is from 1:30 to 30:1.

The invention provides for the industrial gear oil compositions described herein where component (b) is present from 0.1 to 10 percent by weight of the overall industrial gear oil composition, and component (c) is present from 0.1 to 10 percent by weight of the overall industrial gear oil composition.

The invention further provides a process of making any of industrial gear oil compositions described herein, where the process includes the step of: (1) mixing: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid; resulting in an industrial gear oil composition.

The invention further provides a method of improving the friction and/or antiwear properties of an industrial gear oil composition, where the method includes the step of: (1) mixing: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid; resulting in an industrial gear oil composition with improved friction and antiwear properties of the composition. The invention provides a method of improving the friction properties of an industrial gear oil composition. The invention provides a method of improving the antiwear properties of an industrial gear oil composition. The invention provides a method of improving the friction and antiwear properties of an industrial gear oil composition. These methods may be applied to any of the industrial gear oil compositions described herein.

The invention further provides the use of an additive package to improve the friction and/or antiwear properties of an industrial gear oil composition, where the industrial gear oil composition includes (a) an oil of lubricating viscosity; and where the additive package includes (b) a phosphorus-containing compound and (c) a derivative of a hydroxy-carboxylic acid. The invention provides a use of the described additive package to improve the friction properties of an industrial gear oil composition. The invention provides a use of the described additive package to improve the antiwear properties of an industrial gear oil composition. The invention provides a use of the described additive package to improve the friction and antiwear properties of an industrial gear oil composition.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below by way of non-limiting illustration.

The invention provides an industrial gear oil composition that includes: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid.

The Oil of Lubricating Viscosity

The compositions of the invention include an oil of lubricating viscosity.

The oil of lubricating viscosity can be present in a major amount, for a lubricant composition, or in a concentrate forming amount, for a concentrate and/or additive composition. The industrial gear oil compositions of the invention may be either lubricant compositions or concentrate and/or additive compositions.

Suitable oils include natural and synthetic lubricating oils and mixtures thereof. In a fully formulated lubricant, the oil of lubricating viscosity is generally present in a major amount (i.e. an amount greater than 50 percent by weight). Typically, the oil of lubricating viscosity is present in an amount of 75 to 98 percent by weight, and often greater than 80 percent by weight of the overall composition.

The oil of lubricating viscosity may include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined and re-refined oils or mixtures thereof. Unrefined oils are those obtained directly from a natural or synthetic source generally without (or with little) further purification treatment. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Purification techniques are known in the art and include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation and similar processes. Re-refined oils are also known as reclaimed or reprocessed oils, and are obtained by processes similar to those used to obtain refined oils. Re-refined oils are often are processed by techniques directed to removal of spent additives and oil breakdown products.

Natural oils useful as the oil of lubricating viscosity include animal oils and vegetable oils (e.g., castor oil, lard oil), mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic naphthenic types and oils derived from coal or shale or mixtures thereof.

Synthetic oils of lubricating viscosity include hydrocarbon oils such as polymerized and interpolymerised olefins (e.g., polybutylenes, polypropylenes, propyleneisobutylene copolymers); poly(1-hexenes), poly(1-octenes), poly(1-decenes), and mixtures thereof; alkyl-benzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls); alkylated biphenyl ethers and alkylated biphenyl sulfides and the derivatives, analogs and homologs thereof or mixtures thereof. In some embodiments the oil of lubricating viscosity used in the invention is a synthetic oil that includes polymerized polyisobutylene, and in some embodiments the oil of lubricating viscosity used in the invention is a synthetic oil that includes polymerized polyisobutylene and a polyalphaolefin.

Another synthetic oil of lubricating viscosity includes polyol esters other than the hydrocarbyl-capped polyoxyalkylene polyol as disclosed herein, dicarboxylic esters, liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester of decane phosphonic acid), or polymeric tetrahydrofurans. Synthetic conventional oil of lubricating viscosity also includes those produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil of lubricating viscosity may be prepared by a Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may further be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. The five base oil groups are as follows: Group I (sulfur content>0.03 percent by weight, and/or <90 percent by weight saturates, viscosity index 80-120); Group II (sulfur content≦0.03 percent by weight and ≧90 percent by weight saturates, viscosity index 80-120); Group III (sulfur content≦0.03 percent by weight and ≧90 percent by weight saturates, viscosity index≧120); Group IV (all polyalphaolefins, or PAO, such as PAO-2, PAO-4, PAO-5, PAO-6, PAO-7 or PAO-8); and Group V (which encompasses “all others”). The oil of lubricating viscosity includes API Group I, Group II, Group III, Group IV, Group V oil or mixtures thereof. In one embodiment, the oil of lubricating viscosity is an API Group I, Group II, Group III, Group IV oil or mixtures thereof. Alternatively, the oil of lubricating viscosity is often an API Group II, Group III or Group IV oil or mixtures thereof.

In some embodiments the lubricating oil component of the present invention includes a Group II or Group III base oil, or a combination thereof. The oil can also be derived from the hydroisomerization of wax, such as slack wax or a Fischer-Tropsch synthesized wax. Such “Gas-to-Liquid” oils are typically characterized as Group III.

The compositions of the present invention may include some amount of Group I base oils, and even Group IV and Group V base oils. However, in some embodiments the lubricating oil component of the invention contains no more than 20, 10, 5, or even 1 percent by weight Group I base oil. These limits may also apply to Group IV or Group V base oils. In other embodiments the lubricating oil present in the compositions of the invention is at least 60, 70, 80, 90, or even 98 percent by weight Group II and/or Group III base oil. In some embodiments the lubricating oil present in the compositions of the invention is essentially only Group II and/or Group III base oil, where small amounts of other types of base oils may be present but not in amounts that significantly impact the properties or performance of the overall composition.

In some embodiments the compositions of the invention include some amount of Group I and/or Group II base oils. In other embodiments the compositions of the invention are lubricating compositions where the oil of lubricating viscosity is primarily Group I and/or Group II base oils, or even essentially Group I and/or Group II base oils, or even exclusively Group I and/or Group II base oils.

In some embodiments the invention provides a Group II composition, that is the oil of lubricating viscosity includes Group II oil, and can even be primarily if not exclusively Group II oil.

The various described oils of lubricating viscosity may be used alone or in combinations. The oil of lubricating viscosity may be used in the described industrial gear lubricant compositions in the range of about 40 or 50 percent by weight to about 99 percent by weight, or from a minimum of 49.8, 70, 85, 93, 93.5 or even 97 up to a maximum of 99.8, 99, 98.5 or even 97 percent by weight. In other embodiments the oil of lubricating viscosity may be used from a minimum of 40, 65, 73, 73.5, or even 81 up to a maximum of 99.8, 99.7, 98.8, 94.3, 88.5, or even 81 percent by weight.

In still other embodiments the oil of lubricating viscosity may be used from a minimum of 50, 70, 75, 86, 86.8, or even 92.05 up to a maximum of 99.6, 99.5, 98.5, 98.4, or even 98.2 percent by weight, or from a minimum of 80, 90, 95, 96, 96.8, or even 97.05 up to a maximum of 99.6, 99.5, 99.4, or even 99.2 percent by weight, or from 50 to 99.6, from 50 to 99.5, from 70 to 99.5, from 75 to 98.5, from 86 to 98.4, from 86.8 to 98.4, or even from 92.05 to 98.2, and instill further embodiments from 80 to 99.6, from 90 to 99.6, from 95 to 99.5, from 96 to 99.4, from 96.8 to 99.4, or even from 97.05 to 99.2.

The Phosphorus-Containing Compound

The compositions of the invention include a phosphorus containing compound.

The phosphorus containing compound can include a hydrocarbyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or any combination thereof. In some embodiments the phosphorus containing compound includes a hydrocarbyl phosphite, an ester thereof, or a combination thereof. In some embodiments the phosphorus containing compound includes a hydrocarbyl phosphite.

In some embodiments the hydrocarbyl phosphite is an alkyl phosphite. By alkyl it is meant an alkyl group containing only carbon and hydrogen atoms, however either saturated or unsaturated alkyl groups are contemplated or mixtures thereof. In some embodiments the phosphorus containing compound includes an alkyl phosphite that has a fully saturated alkyl group. In some embodiments the phosphorus containing compound includes an alkyl phosphite that has an alkyl group with some unsaturation, for example, one double bond between carbon atoms. Such unsaturated alkyl groups may also be referred to as alkenyl groups, but are included within the term “alkyl group” as used herein unless otherwise noted.

In some embodiments the phosphorus containing compound includes an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or any combination thereof. In some embodiments the phosphorus containing compound includes an alkyl phosphite, an ester thereof, or a combination thereof. In some embodiments the phosphorus containing compound includes an alkyl phosphite.

In some embodiments the phosphorus containing compound includes an alkenyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or any combination thereof. In some embodiments the phosphorus containing compound includes an alkenyl phosphite, an ester thereof, or a combination thereof. In some embodiments the phosphorus containing compound includes an alkenyl phosphite.

In some embodiments the phosphorus containing compound includes dialkyl hydrogen phosphites.

In some embodiments the phosphorus-containing compound is essentially free of, or even completely free of, phosphoric acid esters and/or amine salts thereof.

In some embodiments the phosphorus-containing compound may be described as a fatty phosphite. Suitable phosphites include those having at least one hydrocarbyl group with 4 or more, or 8 or more, or 12 or more, carbon atoms. Typical ranges for the number of carbon atoms on the hydrocarbyl group include 8 to 30, or 10 to 24, or 12 to 22, or 14 to 20, or 16 to 18. The phosphite may be a mono-hydrocarbyl substituted phosphite, a di-hydrocarbyl substituted phosphite, or a tri-hydrocarbyl substituted phosphite. In one embodiment the phosphite is sulphur-free i.e., the phosphite is not a thiophosphite.

The phosphite having at least one hydrocarbyl group with 4 or more carbon atoms may be represented by the formulae:

wherein at least one of R⁶, R⁷ and R⁸ may be a hydrocarbyl group containing at least 4 carbon atoms and the other may be hydrogen or a hydrocarbyl group. In one embodiment R⁶, R⁷ and R⁸ are all hydrocarbyl groups. The hydrocarbyl groups may be alkyl, cycloalkyl, aryl, acyclic or mixtures thereof. In the formula with all three groups R⁶, R⁷ and R⁸, the compound may be a tri-hydrocarbyl substituted phosphite i.e., R⁶, R⁷ and R⁸ are all hydrocarbyl groups and in some embodiments may be alkyl groups

The alkyl groups may be linear or branched, typically linear, and saturated or unsaturated, typically saturated. Examples of alkyl groups for R⁶, R⁷ and R⁸ include octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl or mixtures thereof.

In some embodiments the fatty phosphite component of the invention, and/or the composition overall is essentially free of, or even completely free of phosphoric acid ester and/or amine salts thereof.

In some embodiments the fatty phosphite comprises an alkenyl phosphite or esters thereof, for example esters of dimethyl hydrogen phosphite. The dimethyl hydrogen phosphite may be esterified, and in some embodiments transesterified, by reaction with an alcohol, for example oleyl alcohol.

In some embodiments the fatty phosphite is present at no more than 5 percent by weight, or even at no more than 4, 3, 2, or even 1 percent by weight of the overall industrial gear oil composition. Good overall performance can often be achieved by using such high amounts of the fatty phosphite. One of the main aspects of the present invention is the ability to provide comparable performance with industrial gear oil compositions that contain much lower amounts of fatty phosphite, due to the synergistic benefit received when using the fatty phosphite in combination with the derivative of a hydroxy-carboxylic acid, described herein.

The fatty phosphite may be present in the overall industrial gear lubricant composition from 0.3 to 10 percent by weight, or in other embodiments from a minimum level of 0.3, 0.7, 1, or even 1.2 up to a maximum level of 10, 5, 3, 2.7, 2, 1.5 or even 1.2 percent by weight.

In still other embodiments the fatty phosphite may be present in the overall industrial gear lubricant composition from 0.3 to 10 percent by weight, or from a minimum level of 0.3, 0.4, 0.5, or even 0.7 up to a maximum of 10, 5, 3, 2.7, or even 1.2 percent by weight, or from 0.3 to 10, from 0.3 to 5, from 0.4 to 3, from 0.5 to 3.0, from 0.5 to 2.7, from 0.7 to 2.7, from 0.3 to 1.2, or from 0.5 to 1.2 percent by weight.

The Derivative of a Hydroxy-Carboxylic Acid

The compositions of the invention include a derivative of a hydroxy-carboxylic acid.

Suitable acids may include from 1 to 5 or 2 carboxy groups or from 1 to 5 or 2 hydroxy groups. In some embodiments the friction modifier is derivable from a hydroxy-carboxylic acid represented by the formula:

wherein: a and b may be independently integers of 1 to 5, or 1 to 2; X may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y may be independently —O—, >NH, or >NR³ or two Y's together representing the nitrogen of an imide structure R⁴—N< formed between two carbonyl groups; and each R³ and R⁴ may be independently hydrogen or a hydrocarbyl group, provided that at least one R¹ and R³ group may be a hydrocarbyl group; each R² may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR² group is located on a carbon atom within X that is α or β to at least one of the —C(O)—Y—R¹ groups, and further provided that at least on R² is hydrogen.

The hydroxy-carboxylic acid is reacted with an alcohol and/or an amine, via a condensation reaction, forming the derivative of a hydroxy-carboxylic acid, which may also be referred to herein as a friction modifier additive.

In one embodiment the hydroxy-carboxylic acid used in the preparation of the derivative of a hydroxy-carboxylic acid is represented by the formula:

wherein each R⁵ is independently H or a hydrocarbyl group, or wherein the R⁵ groups together form a ring. In one embodiment, where R⁵ is H, the condensation product is optionally further functionalized by acylation or reaction with a boron compound. In another embodiment the friction modifier is not borated.

In any of the embodiments above, the hydroxy-carboxylic acid may be tartaric acid, citric acid, or combinations thereof, and may also be a reactive equivalent of such acids (including esters, acid halides, or anhydrides). The resulting friction modifiers may include imide, di-ester, di-amide, or ester-amide derivatives of tartaric acid, citric acid, or mixtures thereof. In one embodiment the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid. In one embodiment the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid.

In one embodiment the derivative of hydroxycarboxylic acid includes an ester derivative of tartaric acid. In one embodiment the derivative of hydroxycarboxylic acid includes an imide and/or amide derivative of tartaric acid.

The amines used in the preparation of the friction modifier may have the formula RR′NH wherein R and R′ each independently represent H, a hydrocarbon-based radical of 1 or 8 to 30 or 150 carbon atoms, that is, 1 to 150 or 8 to 30 or 1 to 30 or 8 to 150 atoms. Amines having a range of carbon atoms with a lower limit of 2, 3, 4, 6, 10, or 12 carbon atoms and an upper limit of 120, 80, 48, 24, 20, 18, or 16 carbon atoms may also be used. In one embodiment, each of the groups R and R′ has 8 or 6 to 30 or 12 carbon atoms. In one embodiment, the sum of carbon atoms in R and R′ is at least 8. R and R′ may be linear or branched.

The alcohols useful for preparing the friction modifier will similarly contain 1 or 8 to 30 or 150 carbon atoms. Alcohols having a range of carbon atoms from a lower limit of 2, 3, 4, 6, 10, or 12 carbon atoms and an upper limit of 120, 80, 48, 24, 20, 18, or 16 carbon atoms may also be used. In certain embodiments the number of carbon atoms in the alcohol-derived group may be 8 to 24, 10 to 18, 12 to 16, or 13 carbon atoms.

The alcohols and amines may be linear or branched, and, if branched, the branching may occur at any point in the chain and the branching may be of any length. In some embodiments the alcohols and/or amines used include branched compounds, and in still other embodiments, the alcohols and amines used are at least 50%, 75% or even 80% branched. In other embodiments the alcohols are linear.

In some embodiments, the alcohol and/or amine have at least 6 carbon atoms. Accordingly, certain embodiments of the invention employ the product prepared from branched alcohols and/or amines of at least 6 carbon atoms, for instance, branched C₆₋₁₈ or C₈₋₁₈ alcohols or branched C₁₂₋₁₆ alcohols, either as single materials or as mixtures. Specific examples include 2-ethylhexanol and isotridecyl alcohol, the latter of which may represent a commercial grade mixture of various isomers. Also, certain embodiments of the invention employ the product prepared from linear alcohols of at least 6 carbon atoms, for instance, linear C₆₋₁₈ or C₈₋₁₈ alcohols or linear C₁₂₋₁₆ alcohols, either as single materials or as mixtures.

The tartaric acid used for preparing the tartrates, tartrimides, or tartramides of the invention can be the commercially available type (obtained from Sargent Welch), and it exists in one or more isomeric forms such as d-tartaric acid, l-tartaric acid, d,l-tartaric acid or meso-tartaric acid, often depending on the source (natural) or method of synthesis (e.g. from maleic acid). These derivatives can also be prepared from functional equivalents to the diacid readily apparent to those skilled in the art, such as esters, acid chlorides, anhydrides, etc.

In one embodiment the derivative of a hydroxy-carboxylic acid, which may also be referred to as a friction modifier, can be represented by a compound of the formula:

wherein: n′ is 0 to 10; p is 1 to 5; Y and Y′ are independently —O—, >NH, >NR¹¹, or an imide group formed by the linking of the Y and Y′ groups forming a R¹¹—N< group between two >C═O groups; R⁹ and R¹⁰ are independently hydrocarbyl groups, typically containing 1, 4 or 6 to 150, 30 or 24 carbon atoms; and X is independently —CH₂—, >CHR¹² or >CR¹²R¹³, >CHOR¹⁴, >C(OR¹⁴)CO₂R¹⁴, or >C(CO₂R¹⁴)₂, —CH₃, —CH₂R¹² or —CHR¹²R¹³, CH₂OR¹⁴, or —CH(CO₂R¹⁴)₂, or mixtures thereof wherein: R¹¹ is a hydrocarbyl group; R¹² and R¹³ are independently keto-containing groups (such as acyl groups), ester groups or hydrocarbyl groups; and R¹⁴ is independently hydrogen or a hydrocarbyl group, typically containing 1 to 150 carbon atoms.

In some embodiments the friction modifiers described by the structure above have at least one X that is hydroxyl-containing (e.g., >CHOR¹⁴, wherein R¹⁴ is hydrogen). When X is hydroxyl-containing, the compound may be derived from hydroxy-carboxylic acids such as tartaric acid, citric acid, or mixtures thereof. In one embodiment the compound is derived from citric acid and R⁹ and R¹⁰ contain at least 6 or 8 carbon atoms up to 150, or 6 or 8 to 30 or 24 carbon atoms. In one embodiment the compound is derived from tartaric acid and R⁹ and R¹⁰ contain 4 or 6 to 30 or 24 carbon atoms. When X is not hydroxyl-containing, the compound may be derived from malonic acid, oxalic acid, chlorophenyl malonic acid, or mixtures thereof.

In one embodiment the friction modifier component of the present invention includes oleyl tartrimide, stearyl tartrimide, 2-ethylhexyl tartrimide, or combinations thereof. The friction modifier may be present in the compositions of the present invention at levels of at least 0.1, 0.15, 0.2, 0.3, 0.5 or even 1.0 percent by weight. The friction modifier may be present at amounts up to, or even less than, 10, 9, 8, 7.5, 5, or even 4 or 3 percent by weight.

The compositions of the present invention may optionally include one or more additional friction modifiers. These additional friction modifiers may include esters of polyols such as glycerol monooleates, as well as their borated derivatives; fatty phosphites; fatty acid amides such as oleyl amides; borated fatty epoxides; fatty amines, including borated alkoxylated fatty amines; sulfurized olefins; and mixtures thereof.

Esters of polyols include fatty acid esters of glycerol. These can be prepared by a variety of methods well known in the art. Many of these esters, such as glycerol monooleate and glycerol mono-tallowate, are manufactured on a commercial scale. The esters useful for this invention are oil-soluble and are preferably prepared from C₈ to C₂₂ fatty acids or mixtures thereof such as are found in natural products. The fatty acid may be saturated or unsaturated. Certain compounds found in acids from natural sources may include licanic acid which contains one keto group. Useful C₈ to C₂₂ fatty acids are those of the formula R—COOH wherein R is alkyl or alkenyl.

The fatty acid monoester of glycerol is useful. Mixtures of mono and diesters may be used. Mixtures of mono- and diester can contain at least about 40% of the monoester. Mixtures of mono- and diesters of glycerol containing from about 40% to about 60% by weight of the monoester can be used. For example, commercial glycerol monooleate containing a mixture of from 45% to 55% by weight monoester and from 55% to 45% diester can be used.

Useful fatty acids are oleic, stearic, isostearic, palmitic, myristic, palmitoleic, linoleic, lauric, linolenic, and eleostearic, and the acids from the natural products, such as tallow, palm oil, olive oil, peanut oil. Useful acids and/or oils also include those derived from genetically modified plants, such as canola oil and sunflower oil.

Although tartrates and esters of polyols such as glycerol monooleate may appear to have superficially similar molecular structures, it is observed that certain combinations of these materials may actually provide better performance, e.g., in wear prevention, than either material used alone.

Fatty acid amides have been discussed in detail in U.S. Pat. No. 4,280,916. Suitable amides are C₈-C₂₄ aliphatic monocarboxylic amides and are well known. Reacting the fatty acid base compound with ammonia produces the fatty amide. The fatty acids and amides derived there from may be either saturated or unsaturated. Important fatty acids include lauric acid (C₁₂), palmitic acid (C₁₆), and stearic acid (C₁₈). Other important unsaturated fatty acids include oleic, linoleic and linolenic acids, all of which are C₁₈. In one embodiment, the fatty amides of the instant invention are those derived from the C₁₈ unsaturated fatty acids.

The fatty amines and the diethoxylated long chain amines such as N,N-bis-(2-hydroxyethyl)-tallowamine themselves are generally useful as components of this invention. Both types of amines are commercially available. Fatty amines and ethoxylated fatty amines are described in greater detail in U.S. Pat. No. 4,741,848.

In some embodiments the compositions of the present invention do not include any of these optional friction modifiers and in other embodiments, one or more of any of the optional friction modifiers listed herein are not present in the compositions of the present invention.

In other embodiments an additional friction modifier is present, and that friction modifier is an amide of an aliphatic carboxylic acid containing 6 to 28 carbon atoms. In other embodiments the additional friction modifier is an amide of stearic acid, oleic acid, or combinations thereof.

The derivative of a hydroxy-carboxylic acid may be present in the overall industrial gear lubricant composition from 0.1 to 10 percent by weight, or from a minimum level of 0.1 up to a maximum of 10, 5, 2, 1, 0.5, or even 0.25 percent by weight, or from 0.1 to 10, from 0.1 to 5, from 0.1 to 2, from 0.1 to 1, from 0.1 to 0.5, or even from 0.1 to 0.25 percent by weight.

Additional Additives

The compositions of the invention may further include one or more additional additives, for example the composition of the invention may include an industrial gear additive package. In other words, the compositions of the invention are designed to be industrial gear lubricants, or additive packages for making the same. The present invention does not relate to automotive gear lubricants or other lubricating compositions.

Any combination of conventional additive packages designed for industrial gear application may be used. The invention inherently assumes such additive packages are essentially free of the phosphorus containing compounds and derivatives of hydroxy-carboxylic acids described above, or at least do not contain the type of the phosphorus containing compounds and derivatives of hydroxy-carboxylic acids specified by the particular embodiment of the invention.

The additional additives which may be present in the industrial gear oil compositions of the invention include: a demulsifier, a pour point depressant, an antioxidant, a dispersant, a metal deactivator (such as a copper deactivator), an antiwear agent, an extreme pressure agent, a viscosity modifier, or some mixture thereof. In some embodiments the additives may each be present in the range from 50, 75, 100 or even 150 ppm up to 5, 4, 3, 2 or even 1.5 percent by weight, or from 75 ppm to 0.5 percent by weight, from 100 ppm to 0.4 percent by weight, or from 150 ppm to 0.3 percent by weight, where the percent by weight values are with regards to the overall lubricating oil composition. However it is noted that some additives, including viscosity modifying polymers, which may alternatively be considered as part of the base fluid, may be present in higher amounts including up to 30, 40, or even 50% by weight when considered separate from the base fluid. Each of the described additional additives may be used alone or as mixtures thereof.

Antifoams, also known as foam inhibitors, are known in the art and include but are not limited to organic silicones and non-silicon foam inhibitors. Examples of organic silicones include dimethyl silicone and polysiloxanes. Examples of non-silicon foam inhibitors include but are not limited to polyethers, polyacrylates and mixtures thereof as well as copolymers of ethyl acrylate, 2-ethylhexylacrylate, and optionally vinyl acetate. In some embodiments the antifoam is a polyacrylate. Antifoams may be present in the composition from 0.001 to 0.012 or 0.004 pbw or even 0.001 to 0.003 pbw.

Demulsifiers are known in the art and include but are not limited to derivatives of propylene oxide, ethylene oxide, polyoxyalkylene alcohols, alkyl amines, amino alcohols, diamines or polyamines reacted sequentially with ethylene oxide or substituted ethylene oxides or mixtures thereof. Examples of demulsifiers include polyethylene glycols, polyethylene oxides, polypropylene oxides, (ethylene oxide-propylene oxide) polymers and mixtures thereof. In some embodiments the demulsifiers are polyethers. Demulsifiers may be present in the composition from 0.002 to 0.2 pbw.

Pour point depressants are known in the art and include but are not limited to esters of maleic anhydride-styrene copolymers, polymethacrylates; polyacrylates; polyacrylamides; condensation products of haloparaffin waxes and aromatic compounds; vinyl carboxylate polymers; and terpolymers of dialkyl fumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers and mixtures thereof.

The compositions of the invention may also include a rust inhibitor, other than some of the additives described above. Suitable rust inhibitors include hydrocarbyl amine salts of dialkyldithiophosphoric acid, hydrocarbyl amine salts of hydrocarbyl arenesulphonic acid, fatty carboxylic acids or esters thereof, an ester of a nitrogen-containing carboxylic acid, an ammonium sulfonate, an imidazoline, mono-thio phosphate salts or esters, or any combination thereof; or mixtures thereof. Examples of hydrocarbyl amine salts of dialkyldithiophosphoric acid of the invention include but are not limited to those described above, as well as the reaction product(s) of diheptyl or dioctyl or dinonyl dithiophosphoric acids with ethylenediamine, morpholine or Primene™ 81R or mixtures thereof. Suitable hydrocarbyl amine salts of hydrocarbyl arenesulphonic acids used in the rust inhibitor package of the invention are represented by the formula:

wherein Cy is a benzene or naphthalene ring. R¹⁵ is a hydrocarbyl group with about 4 to about 30, preferably about 6 to about 25, more preferably about 8 to about 20 carbon atoms. z is independently 1, 2, 3, or 4 and most preferably z is 1 or 2. R¹⁶, R¹⁷ and R¹⁸ are the same as described above. Examples of hydrocarbyl amine salts of hydrocarbyl arenesulphonic acid of the invention include but are not limited to the ethylenediamine salt of dinonylnaphthalene sulfonic acid. Examples of suitable fatty carboxylic acids or esters thereof include glycerol monooleate and oleic acid. An example of a suitable ester of a nitrogen-containing carboxylic acid includes oleyl sarcosine. The rust inhibitors may be present in the range from 0.02 to 0.2, from 0.03 to 0.15, from 0.04 to 0.12, or from 0.05 to 0.1 percent by weight of the lubricating oil composition. The rust inhibitors of the invention may be used alone or in mixtures thereof.

The compositions of the invention may also include a metal deactivator. Metal deactivators are used to neutralise the catalytic effect of metal for promoting oxidation in lubricating oil. Suitable metal deactivators include but are not limited to triazoles, tolyltriazoles, a thiadiazole, or combinations thereof, as well as derivatives thereof. Examples include derivatives of benzotriazoles other than those described above, benzimidazole, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N′-dialkyldithio-carbamoyl)benzothiazoles, 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles, 2,5-bis(N,N′-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercapto thiadiazoles or mixtures thereof. These additives may be used from 0.01 to 0.25 percent by weight in the overall composition. In some embodiments the metal deactivator is a hydrocarbyl substituted benzotriazole compound. The benzotriazole compounds with hydrocarbyl substitutions include at least one of the following ring positions 1- or 2- or 4- or 5- or 6- or 7-benzotriazoles. The hydrocarbyl groups contain about 1 to about 30, preferably about 1 to about 15, more preferably about 1 to about 7 carbon atoms, and most preferably the metal deactivator is 5-methylbenzotriazole used alone or mixtures thereof. The metal deactivators may be present in the range from 0.001 to 0.5, from 0.01 to 0.04 or from 0.015 to 0.03 pbw of the lubricating oil composition. Metal deactivators may also be present in the composition from 0.002 or 0.004 to 0.02 pbw. The metal deactivator may be used alone or mixtures thereof.

Antioxidants may also be present including (i) an alkylated diphenylamine, and (ii) a substituted hydrocarbyl mono-sulfide. In some embodiments the alkylated diphenylamines of the invention are bis-nonylated diphenylamine and bis-octylated diphenylamine. In some embodiments the substituted hydrocarbyl monosulfides include n-dodecyl-2-hydroxyethyl sulfide, 1-(tert-dodecylthio)-2-propanol, or combinations thereof. In some embodiments the substituted hydrocarbyl monosulfide is 1-(tert-dodecylthio)-2-propanol. The antioxidant package may also include sterically hindered phenols. Examples of suitable hydrocarbyl groups for the sterically hindered phenols include but are not limited to 2-ethylhexyl or n-butyl ester, dodecyl or mixtures thereof. Examples of methylene-bridged sterically hindered phenols include but are not limited to 4,4′-methylene-bis(6-tert-butyl o-cresol), 4,4′-methylene-bis(2-tert-amyl-o-cresol), 2,2-methylene-bis(4-methyl-6-tert-butylphenol), 4,4′-methylene-bis(2,6-di-tertbutylphenol) or mixtures thereof.

In some embodiments the additional additives present include a nitrogen-containing dispersant, for example a hydrocarbyl substituted nitrogen containing additive. Suitable hydrocarbyl substituted nitrogen containing additives include ashless dispersants and polymeric dispersants. Ashless dispersants are so-named because, as supplied, they do not contain metal and thus do not normally contribute to sulfated ash when added to a lubricant. However they may, of course, interact with ambient metals once they are added to a lubricant which includes metal-containing species. Ashless dispersants are characterized by a polar group attached to a relatively high molecular weight hydrocarbon chain. Examples of such materials include succinimide dispersants, Mannich dispersants, and borated derivatives thereof.

In some embodiments the additional additives present include a sulfur-containing compound. Such sulfur-containing compounds may include sulfurized olefins and polysulfides and/or sulfurized fatty esters. The sulfurized olefin or polysulfides may be derived from isobutylene, butylene, propylene, ethylene, or some combination thereof. The sulfurized fatty esters may include sulfurized olefins derived from any of the natural oils or synthetic oils described above, or even some combination thereof. For example the sulfurized fatty ester may be derived from vegetable oil.

In some embodiments the invention includes a sulfurized fatty ester that includes a sulfurized natural oil. In some embodiments the sulfurized fatty ester includes a sulfurized animal and/or vegetable oil. In some embodiments the sulfurized fatty ester includes a sulfurized vegetable oil. In some embodiments the sulfurized fatty ester includes a sulfurized unsaturated oil. In some embodiments the sulfurized fatty ester includes a sulfurized unsaturated natural oil. In some embodiments the sulfurized fatty ester includes a sulfurized unsaturated vegetable oil. In some embodiments the sulfurized fatty ester described above further includes one or more sulfurized olefins and/or polysulfides. In some embodiments the sulfurized fatty ester includes a sulfurized rapeseed oil.

In some embodiments the additional additives present include one or more phosphorous amine salts (different from the phosphorous containing compound described above), but in amounts such that the resulting industrial gear lubricant compositions, contains no more than 1.0 percent by weight of such materials, or even no more than 0.75 or 0.6 percent by weight. In other embodiments the resulting industrial gear lubricant compositions, are essentially free of or even completely free of such phosphorous amine salts.

In some embodiments the additional additive component includes one or more antiwear additives and/or extreme pressure agents, one or more rust and/or corrosion inhibitors, one or more foam inhibitors, one or more demulsifiers, or any combination thereof. In other embodiments the additional additives, and/or the resulting industrial gear lubricant compositions, are essentially free of or even completely free of phosphorous amine salts, dispersants, or both.

In some embodiments the additional additives, and/or the resulting industrial gear lubricant compositions, include a demulsifier, a corrosion inhibitor, a friction modifier, or combination of two or more thereof. In some embodiments the corrosion inhibitor includes a tolyltriazole. In still other embodiments the additional additive component, and/or the resulting industrial gear lubricant compositions, include one or more sulfurized olefins or polysulfides; one or more phosphorus amine salts; one or more thiophosphate esters, one or more thiadiazoles, tolyltriazoles, polyethers, and/or alkenyl amines; one or more ester copolymers; one or more carboxylic esters; one or more succinimide dispersants, or any combination thereof.

In some embodiments the compositions of the invention further include (d), one or more additional additives, that may include one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkyl and/or alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, hydrocarbon polymers, or any combination thereof.

Dispersants suitable for use in the compositions of the invention are not overly limited and may include borated dispersants, non-borated dispersants, succinimide dispersants (including borated and non-borated succinimide dispersants), Mannich dispersants, and the like.

In some embodiments the compositions of the invention are free of antioxidants. In some embodiments the compositions of the invention are free of fatty amines. In some embodiments the compositions of the invention are free of high TBN overbased detergents (where high TBN can mean having a TBN of >100, >50, >20 or even >10). In some embodiments the compositions of the invention are free of zinc dithiophosphates.

In some embodiments the compositions of the invention, in addition to the components (a), (b), and (c), further comprise a sulfurized olefin, a dithiothiophosphate ester, a phosphate amine salt, a high TBN succinimide dispersant, a fatty amine, a tolyltriazole, an acrylate, a polyether, and a thiadiazole, which may be described as additional component (d).

In some embodiments the compositions of the invention, in addition to the components (a), (b), and (c), further comprise an extreme pressure agent, an combination of antiwear agents, a rust inhibitor, a metal deactivator, a antifoam agent, a demulsifier, and a copper deactivator, which may be described as additional component (d).

The additional additives may be present in the overall industrial gear lubricant composition from 0.1 to 30 percent by weight, or from a minimum level of 0.1, 1 or even 2 percent by weight up to a maximum of 30, 20, 10, 5, or even 2 percent by weight, or from 0.1 to 30, from 0.1 to 20, from 1 to 20, from 1 to 10, from 1 to 5, or even about 2 percent by weight. These ranges and limits may be applied to each individual additional additive present in the composition, or to all of the additional additives present.

INDUSTRIAL APPLICATION

As noted above the invention includes both industrial gear lubricant compositions and industrial gear additive concentrate compositions that may be used to make industrial gear lubricant compositions.

The various ranges for the components described above can be applied to concentrate compositions by maintaining the same relative ratios between components (b), (c), and (d) when present, while adjustment the amount of (a), (that is the amount of (a) will be much lower in a concentrate composition compared to a lubricant composition). In such embodiments the percent by weight values for components (b), (c), and (d) when present may be treated as parts by weight (pbw), with oil making up the balance of the concentrate composition, including anywhere from 0 or 0.1 or 0.5 or even 1 pbw up to 10, 20, 30 or even 40 or 50 pbw oil and/or base fluid.

In the compositions of the invention it may be useful in some embodiments to specify the weight ratio of component (b), the phosphorus containing compound relative to component (c), the sulfurized fatty ester. In some embodiments the weight ratio of component (b) to component (c) is from 2.5:1 to 30:1, or from 2.5:1 to 12:1, or from 3:1 to 12:1. The ratios may also be in a range selecting a minimum and maximum amount from any of the following points: to or from 2.8:1, to or from 3.1:1, to or from 3.6:1, to or from 4.6:1, to or from 5.1:1, to or from 6.1:1, to or from 7.1:1, to or from 10.8:1, to or from 12.1:1, to or from 27.1:1. These ratios may apply to the industrial gear lubricant compositions of the invention and/or to the industrial gear additive concentrate compositions of the invention.

In some embodiments the of the invention component (b) and (c) are present in amounts such that the total combined treat rate of components (b) and (c) in the industrial gear lubricant compositions is at least 0.70 percent by weight.

In some embodiments the industrial gear lubricant compositions of the invention will provide a wear scar diameter, as measured by HFRR (see details on the testing conditions below), of no more than 360 micrometer, and in other embodiments of no more than 340 micrometer, no more than 337 micrometer, and even from 200 or 240 to 357, 340, or 337 micrometer.

In some embodiments the industrial gear lubricant compositions of the invention will provide a coefficient of friction, as measured by HFRR (see details on the testing conditions below), of no more than 0.115, and even from 0.05 to 0.115.

The invention includes methods of improving the friction and/or antiwear properties of an industrial gear oil composition. The method includes the step of: (1) adding to an industrial gear oil composition, which includes (a) the oil of lubricating viscosity, the following components: (b) the phosphorus-containing compound; and (c) the derivative of a hydroxy-carboxylic acid; resulting in an industrial gear oil composition with friction and/or antiwear properties. In some embodiments the methods provide improved friction properties. In some embodiments the methods provide improved antiwear properties. In some embodiments the methods provide improved friction and antiwear properties.

The invention includes the use of the described industrial gear oil composition to improve the friction and/or antiwear performance of an industrial gearbox.

The invention also includes the use of an additive package to improve the friction and antiwear properties of an industrial gear oil composition where the industrial gear oil composition includes (a) an oil of lubricating viscosity, and where the additive package includes (b) a phosphorus-containing compound and (c) a derivative of a hydroxy-carboxylic acid.

The improvements noted above are in regards to the same industrial gear oil composition missing one or both of the components (b) and (c), which when used together in an industrial gear oil composition, provide synergistic benefits.

The amount of each chemical component described is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, that is, on an active chemical basis, unless otherwise indicated. However, unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

-   -   hydrocarbon substituents, that is, aliphatic (e.g., alkyl or         alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)         substituents, and aromatic-, aliphatic-, and         alicyclic-substituted aromatic substituents, as well as cyclic         substituents wherein the ring is completed through another         portion of the molecule (e.g., two substituents together form a         ring);     -   substituted hydrocarbon substituents, that is, substituents         containing non-hydrocarbon groups which, in the context of this         invention, do not alter the predominantly hydrocarbon nature of         the substituent (e.g., halo (especially chloro and fluoro),         hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and         sulfoxy);     -   hetero substituents, that is, substituents which, while having a         predominantly hydrocarbon character, in the context of this         invention, contain other than carbon in a ring or chain         otherwise composed of carbon atoms and encompass substituents as         pyridyl, furyl, thienyl and imidazolyl. Heteroatoms include         sulfur, oxygen, and nitrogen. In general, no more than two, or         no more than one, non-hydrocarbon substituent will be present         for every ten carbon atoms in the hydrocarbyl group;         alternatively, there may be no non-hydrocarbon substituents in         the hydrocarbyl group.

It is known some of the materials described above may interact in the final formulation, so that components of the final formulation may be different from those initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other acidic or anionic sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the invention; the invention encompasses the composition prepared by admixing the components described above.

The invention may be better understood with reference to the following non-limiting examples.

Examples

A set of examples is prepared and tested in order to demonstrate the benefits of the invention. The formulations of the examples are summarized in the table below.

Examples 1 to 13 are comparative examples. Each example is either missing component (b) or component (c), or it does not contain enough component (b) in combination with component (c) to produce the benefits of the invention. Examples 14 to 30 are inventive examples.

Each of the examples are tested using a HFRR (high frequency reciprocating rig) test stand with equipment as defined in ASTM D6079. Conditions for the testing are: a 700 gram load, 100 Hertz frequency, 0.5 mm stroke length, steady state (isothermal) operation at 100° C. The wear scar diameter, measured in micrometers and the coefficient of friction (COF) are collected for two runs for each sample. Lower wear scar values and lower COF values indicate improved wear performance. The results collected from the testing are summarized in the table below, with average values reported for the wear scar and COF.

TABLE 1 Example Formulations and HFRR Results¹ Comp(b) Comp(b) Comp(c) Comp(c) ADD ADD ADD ADD Comp(d) Exam- Comp(a) B-1³ B-2⁴ C-1⁵ C-2⁶ ADD Wear ple No. OIL² 134.51 134.50 0744.5 0744.7 PACK⁷ (mm) COF 1 98.0 0.21 0 0 0 1.79 339.5 0.117 2 95.5 0 2.71 0 0 1.79 472.5 0.071 3 97.9 0.21 0 0.1 0 1.79 363.5 0.126 4 97.9 0.21 0 0 0.1 1.79 358 0.108 5 97.6 0.61 0 0 0 1.79 355 0.102 6 97.7 0.46 0 0.1 0 1.79 354 0.126 7 97.8 0.46 0 0 0 1.79 353.5 0.127 8 97.7 0.51 0 0 0 1.79 352.5 0.117 9 97.9 0.31 0 0 0 1.79 346.5 0.115 10 97.5 0.71 0 0 0 1.79 346.5 0.108 11 97.8 0.31 0 0 0.1 1.79 343.5 0.123 12 97.7 0.46 0 0 0.1 1.79 343.5 0.123 13 97.8 0.31 0 0.1 0 1.79 336.5 0.132 14 96.3 0 1.96 0 0 1.79 275 0.077 15 97.0 1.21 0 0 0 1.79 253 0.075 16 96.3 1.96 0 0 0 1.79 248.5 0.084 17 95.5 2.71 0 0 0 1.79 245.5 0.075 18 97.5 0.56 0 0.2 0 1.79 318 0.087 19 97.5 0.61 0 0.1 0 1.79 315 0.084 20 97.6 0.51 0 0 0.1 1.79 308.5 0.084 21 97.3 0.71 0 0.2 0 1.79 294 0.062 22 97.3 0.71 0 0 0.2 1.79 285 0.059 23 97.5 0.61 0 0 0.1 1.79 276 0.063 24 97.5 0.56 0 0 0.2 1.79 268 0.056 25 96.9 1.21 0 0 0.1 1.79 266 0.056 26 95.4 2.71 0 0 0.1 1.79 262 0.067 27 97.4 0.71 0 0.1 0 1.79 277 0.068 28 97.4 0.71 0 0 0.1 1.79 254.75 0.060 29 95.3 2.71 0 0 0.25 1.79 252 0.075 30 96.9 1.21 0 0.1 0 1.79 243.5 0.082 1—All values in the table above are percent by weigh unless otherwise noted. 2—Component (a) for all the examples is a Group II, ISO 150 base oil. 3—Additive B-1 is a dialkyl phosphite with alkyl groups containing 18 carbon atoms. 4—Additive B-2 is a dialkyl phosphite with alkyl groups containing 16 to 18 carbon atoms. 5—Additive C-1 is an ester derivative of tartaric acid. 6—Additive C-2 is an imide derivative of tartaric acid. 7—The additive pack used in all of the examples includes an extreme pressure agent, a combination of antiwear agents, a rust inhibitor, a metal deactivator, a antifoam agent, a demulsifier, and a copper deactivator.

The results show that the compositions of the invention provide surprisingly improved performance as shown by the HFRR results.

Comparative example 1 is a baseline example with only a small amount (less than 0.3 percent by weight) of component (b) present and no component (c) present at all. All of the inventive examples have a better wear result and a better COF than Example 1.

Comparative examples 3 to 13 either contain an insufficient amount of component (b), an insufficient amount of the combination of component (b) and component (c), or no component (c) at all. All of the inventive examples have a better wear result, a better COF, or both, when compared to Examples 3 to 13.

Comparative examples 2 and 14 to 17 are comparative examples that show what high levels of component (b) are required to achieve results similar to those made possible by the present invention. Even with such high treat rates, comparative example 2 still gives a poor wear result. Comparative examples 14 to 17 give good wear and COF results but only with a very high treat rate of component (b).

Inventive examples 18 to 30 show that when the combination of components (b) and (c) are used in the proper way (a sufficient amount of component (b) and a sufficient total amount of both components together) a synergistic benefit is seen, and this benefit is demonstrated by the examples above to occur with different examples of component (b) and different examples of component (c), over a wide range of treat rates.

Each of the documents referred to above is incorporated herein by reference, including any prior applications, whether or not specifically listed above, from which priority is claimed. The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.

As used herein, the transitional term “comprising,” which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended and does not exclude additional, un-recited elements or method steps. However, in each recitation of “comprising” herein, it is intended that the term also encompass, as alternative embodiments, the phrases “consisting essentially of” and “consisting of,” where “consisting of” excludes any element or step not specified and “consisting essentially of” permits the inclusion of additional un-recited elements or steps that do not materially affect the basic and novel characteristics of the composition or method under consideration.

While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. In this regard, the scope of the invention is to be limited only by the following claims. 

1. An industrial gear oil composition comprising: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid; where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more.
 2. The industrial gear oil composition of claim 1, wherein the oil of lubricating viscosity comprises a mineral base oil.
 3. The industrial gear oil composition of claim 1, wherein the oil of lubricating viscosity comprises a synthetic base oil.
 4. The industrial gear oil composition of claim 1, wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, phosphonates, or some combination thereof.
 5. The industrial gear oil composition of claim 1, wherein the phosphorus-containing compound comprises alkyl phosphites.
 6. The industrial gear oil composition of claim 1, wherein (c), the derivative of a hydroxy-carboxylic acid, comprises a compound derived from a hydroxy-carboxylic acid represented by the formula:

wherein: a and b may be independently integers of 1 to 5; X may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y may be independently —O—, >NH, or >NR³ or two Y's together representing the nitrogen of an imide structure R⁴—N< formed between two carbonyl groups; and each R³ and R⁴ may be independently hydrogen or a hydrocarbyl group, provided that at least one R¹ and R³ group may be a hydrocarbyl group; each R² may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR² group is located on a carbon atom within X that is α or β to at least one of the —C(O)—Y—R¹ groups, and further provided that at least on R² is hydrogen.
 7. The composition of claim 1, wherein (c), the derivative of a hydroxy-carboxylic acid, comprises a compound derived from a hydroxy-carboxylic acid represented by the formula:

wherein each R⁵ is independently H or a hydrocarbyl group, or wherein the R⁵ groups together form a ring; where the hydroxy-carboxylic acid is reacted with an alcohol and/or an amine, via a condensation reaction, to form the derivative of the hydroxy-carboxylic acid.
 8. The composition of claim 1, wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid.
 9. The industrial gear oil composition of claim 1, wherein the composition further comprises (d), one or more additional additives; wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.
 10. The industrial gear oil composition of claim 1, wherein the weight ratio of component (b) to component (c) in the industrial gear oil composition is from 2.5:1 to 30:1.
 11. The industrial gear oil composition of claim 1, wherein component (b) is present from 0.3 to 10 percent by weight of the overall industrial gear oil composition; and wherein component (c) is present from 0.1 to 10 percent by weight of the overall industrial gear oil composition.
 12. A process of making an industrial gear oil composition comprising the step of: (1) mixing the following components: (a) an oil of lubricating viscosity; (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid; where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more; resulting in an industrial gear oil composition.
 13. The process of claim 11, wherein the oil of lubricating viscosity comprises a mineral base oil, a synthetic base oil, or a combination thereof; wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or some combination thereof; wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid; and wherein step (1) optionally further comprises mixing (d), one or more additional additives into the industrial gear oil composition; wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.
 14. A method of improving the friction and antiwear properties of an industrial gear oil composition comprising the step of: (1) adding to an industrial gear oil composition, which comprises (a) an oil of lubricating viscosity, the following components: (b) a phosphorus-containing compound; and (c) a derivative of a hydroxy-carboxylic acid; where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more; resulting in an industrial gear oil composition with improved friction and antiwear properties of the composition.
 15. The method of claim 13, wherein the oil of lubricating viscosity comprises a mineral base oil, a synthetic base oil, or a combination thereof; wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or some combination thereof; wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid; and wherein step (1) optionally further comprises mixing (d), one or more additional additives into the industrial gear oil composition; wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.
 16. (canceled) 